1. Field of the Invention
The present invention generally relates to a non-uniform transmission line, and more particularly to a non-uniform transmission line which may be used as a multi-purpose transmission line.
2. Description of the Related Art
Conventional uniform transmission lines are formed of conductors (e.g., round wires) which have a uniform cross sectional thickness (e.g., diameter) along the length of the line. In addition, the spacings between these uniform conductors are typically constant along the length of the transmission line. Indeed, even in a conventional line having twisted round wires the spacing between the conductors is constant along the length of the line.
The signal integrity of high speed electrical signals, such as digital signals or high bandwidth analog signals as they propagate along such conventional transmission media, is bounded by the electromagnetic characteristics of that cable or transmission media. To date, those characteristics are determined utilizing round wire (e.g., a uniform transmission line) with a defined insulation thickness twisted in a specified fashion and bundled with other wires similarly specified, or by utilizing a coaxial (e.g., two concentric conductors) construction geometry with an appropriate dielectric between the conductors. The characteristic impedance (common mode and differential mode) and its constituents (series resistance and inductance, and shunt capacitance and conductance), cross talk, delay, attenuation and a multiplicity of other parameters are all determined by this physical construction. Thus, these construction techniques limit the cable/transmission media performance, and consequently, put a limit on signal integrity performance.
Further, conventional metallic data wire configurations are trying to get beyond the 250 MHz per pair milestone proposed by the TIA/EIA Category 6 specification. Cable Television/Digital Signal coaxial cable is also limited in transmission capabilities due to its inherent properties and construction.
The maximum performance capabilities of both types of wire (conventional/CATV) are severely degraded in xe2x80x9creal worldxe2x80x9d installations of the cables and the interconnect interfaces. Specifically, the manner in which cables and transmission lines are installed throughout a residential or commercial building""s ceiling, floors and walls induces mechanical distortions with respect to as-manufactured conductor proximities. These physical distortions result in inconsistent electromagnetic properties, adversely affecting signal integrity.
Further, multiple connection interfaces are commonly found along any given signal path between a building""s transmission line entry point to the final destination interconnects and ultimately to the device connection within that building. These multiple connection interfaces result in impedance mismatches causing farther signal degradation.
In addition, conventional wire connectors are made of a conductive material slightly conformed and placed within a close proximity utilizing various forms of fastening to create pressure for the desired effect of electrical connectivity and mechanical stability. These conventional connectors suffer from several problems including varying contact resistance upon installation, changing contact resistance over time, loss of signal, corrosion, difficulty of installation, and disconnection under various mechanical conditions.
The conductor of the transmission line (e.g., wire) also plays a major role in these connector problems due to its inherent structure and incompressibility. Either solid or stranded wire must be formed to properly fasten to a connector. Although it is formed in some fashion, wire still does not make good surface contact. To minimize this effect, users often resort to welding or soldering to make more surface contact available only to find that the next connection has contributed the same issue or even a worse problem, not to mention making the connection irreversible.
In view of the foregoing and other problems of the conventional techniques, an object of the present invention is to provide a non-uniform transmission line which may be used, for example, as a multipurpose transmission medium (e.g., voice/data wire). The applications for the inventive transmission line are virtually limitless but may include, for example, telecommunication systems and signal broadcasting systems. The inventive transmission line may also used, either alone or in combination with other transmission media, as part of an infrastructure (e.g., building) bus.
In a first aspect, the present invention includes a non-uniform transmission line which has at least one patterned conductive layer, a dielectric layer adjacent to the patterned conductive layer(s), and an insulating layer surrounding the patterned conductive layer(s) and the dielectric layer.
The dielectric layer may also be patterned and may have a thickness of about 0.00025 to 0.250 inches and a dielectric constant of 1 to 10. In addition, the dielectric layer may be formed of a polymer and may include a plurality of dielectric layers.
Further, the non-uniform transmission line may include a plurality of patterned conductive layers and a dielectric layer may be formed between each patterned conductive layer. For instance, the plurality of patterned conductive layers may have a multi-planar arrangement and include a first conductive layer in a first horizontal plane, and a second conductive layer in a second horizontal plane.
In addition, the non-uniform transmission line may be flexible. Moreover, when the non-uniform transmission line is flexed, a separation distance may be maintained between each patterned conductive layer.
Further, the patterned conductive layer may be electrically conductive and have a non-uniform pattern within a given period. A period may be defined as the shortest or smallest unique geometrical element or unit cell, that when repeated, makes up the non-uniform transmission line, or alternatively, the shortest non-zero distance, T, in any units, along the length of the non-uniform transmission line such that the cross-section at any arbitrary fixed point, x, along the line, and the cross-section at x+/xe2x88x92T (e.g., x plus or minus T) are identical. Further, each patterned conductive layer may be formed of a variety of electrically conductive materials and have a thickness of no more than about 0.1 inches.
In another aspect, the non-uniform transmission line includes at least one transmission group, each transmission group comprising at least one patterned conductive layer, a dielectric layer formed adjacent the patterned conductive layer(s), and an insulating layer covering the transmission group(s) and dielectric layer. Specifically, the each transmission group may include a plurality of patterned conductive layers with the dielectric layer formed between each patterned conductive layer.
Further, the inventive non-uniform transmission line may include a plurality of transmission groups. For example, the transmission groups may be coplanar, and the dielectric layer may be formed between patterned conductive layers of each transmission group.
In addition, the plurality of transmission groups may be in separate planes so as to form a multi-planar arrangement. In this case a separating insulating layer may be formed between each transmission group to reduce crosstalk between the transmission groups.
Further, the non-uniform transmission group may have a first transmission group with a period (e.g., crossover frequency) which is different from a period of a second transmission group. Further, the transmission groups may be arranged so that the periods of the transmission groups do not coincide. In other words, at one point in the line one transmission group may have a crossover node, whereas another transmission group at the same point in the line may not have a crossover node. Further, the transmission groups may have different applications.
Further, the non-uniform transmission line may include several layers of transmission groups. For instance, the non-uniform transmission line may include a first set of transmission groups, each transmission group having a first patterned conductive layer in a first horizontal plane and a second patterned conductive layer in a second horizontal plane, a second set of transmission groups, each transmission group having a first patterned conductive layer in a third horizontal plane and a second patterned conductive layer in a fourth horizontal plane, and a separating insulating layer formed between the first and second set of transmission groups. In this case, the same dielectric layer is formed between patterned conductive layers in the first set of transmission groups, and the same dielectric layer is formed between patterned conductive layers in the second set of transmission groups.
In addition, the non-uniform transmission line may include a single patterned conductive layer comprising first and second portions which are separated by a predetermined distance, and an insulating layer surrounding the patterned conductive layer. Specifically, the first and second portions may have, for example, interweaving or interlocking arrangement. Further, the patterned conductive layer may have a width of 0.25 inches or more.
In another aspect, a method of fabricating a non-uniform transmission line includes forming at least one patterned conductive layer, forming a dielectric layer adjacent (e.g., between) to each patterned conductive layer, and covering the patterned conductive layer(s) and dielectric layer with an insulating layer. For example, the patterned conductive layer may be formed by a stamping or forming process, etching process, screening process or molding process. Further, the patterned conductive layer may be formed by a laser cutting process, a wafer cutting process and a wafer splitting process.
In another aspect, a bundled transmission line may include at least one non-uniform transmission line which has at least one patterned conductive layer, a dielectric layer adjacent to the patterned conductive layer(s), and an insulating layer surrounding the patterned conductive layer(s) and the dielectric layer. The bundled transmission line may also include at least one uniform transmission line (e.g., round wire).
With its unique and novel features, the present invention provides a revolutionary, new and novel non-uniform transmission line which may be efficiently and effectively used as a high speed transmission medium in multiple and diverse applications.